1. Field of the Invention
The present invention relates to electric propulsion systems and more particularly to a propulsion system powered by a plurality of electric motors.
2. Discussion of the Related Art
For over a century, internal combustion engines have been a mainstay of portable or mobile propulsion systems. These engines have powered everything from automobiles to watercraft to airplanes. Additionally, these internal combustion engines have also been used to power various configurations of stationary machinery. In short, much of a person's everyday life is impacted by powered machines that are directly or indirectly linked to internal combustion engines.
Internal combustion engines possess many disadvantages. First, they are quite noisy and require substantial noise insulation if located in proximity to areas inhabited by humans for even brief periods of time. Further, internal combustion engines utilize fossil fuels that are pollutants if spilled or not handled in a correct manner. The combustion byproducts are also pollutants by injecting excess carbon dioxide, carbon monoxide, nitrous oxides, and forms of sulfur into the atmosphere. While strides have been made to reduce these pollutants, they will always be present in some quantity as a result of the burning of the fuel.
The majority of vehicles are powered by internal combustion engines and most often by a single internal combustion engine. Internal combustion engines are also inherently inefficient and thus require a substantial housing space with associated ventilation and insulation requirements. Even though the reliability of internal combustion engines has improved dramatically over the years, most vehicles are powered by only a single engine. The engine thus represents a single point of failure which can have disastrous and even life threatening results in the event of the engine failing. Further, in the event of a massive failure of the engine requiring its replacement, instead of the repair of a component, the engine must be removed from the vehicle. Often, this poses a very difficult and time-consuming effort resulting in considerable expense and downtime for the vehicle.
One solution has been the replacement of the internal combustion engine with an electric motor. However, electric motors also have some of the same disadvantages as the internal combustion engine. Typically, a single motor is used to provide driving power to each power output such as a single motor to drive each wheel of a car or the propeller of a watercraft. In those applications where a significant power output is required, a very large electric motor is required to provide such power. Again, a single motor equates to a single failure point. Additionally, as the power requirement increases, the size and weight of the electric motor also increases resulting in many of the same housing and replacement problems as an internal combustion engine.
Thus what is desired is an electric propulsion system that minimizes the probability of a single point failure while simultaneously being space adaptable and easy to repair and maintain.